The invention concerns generally the protocol structures that are used to arrange the communication between a mobile terminal and a packet-switched network. Especially the invention concerns the optimal composition of such structures and the arrangement of negotiations where the protocol-determined parameters relating to the communication are agreed upon.
FIG. 1 illustrates the known data protocol stacks that are applied in a packet-switched communication connection where one end is a Mobile Station (MS) and the communication takes place over a GPRS network (General Packet Radio Service) through a Base Station Subsystem (BSS), a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN). The protocol layers where the peer entities are in the MS and the BSS are the physical layer 101 that employs the GSM cellular radio system (Global System for Mobile telecommunications), the Media Access Control (MAC) layer 102 and the Radio Link Control layer 103 which sometimes is regarded as only a part of the MAC layer 102xe2x80x94hence the dashed line between them. The protocol layers where the peer entities are in the BSS and the SGSN are the L1bis layer 104, the Network Service layer 105 and the BSS GPRS Protocol (BSSGP) layer 106.
The layers for which the peer entities are in the MS and the SGSN are the Logical Link Control (LLC) layer 107 and the SubNetwork Dependent Convergence Protocol (SNDCP) layer 108. It should be noted that only data or user plane protocols are shown in FIG. 1; a complete illustration of protocols would include the Layer 3 Mobility Management (L3MM) and Short Message Services (SMS) blocks on top of the LLC layer 107 in parallel with the SNDCP layer 108. Additionally there are the known Session Management (SM) and Radio Resource management (RR) entities that are not located on top of the LLC layer. At the interface between the SGSN and the GGSN there are the Layer 1 (L1) layer 109, the Layer 2 (L2) layer 110, a first Internet Protocol (IP) layer 111, the User Datagram Protocol/Transport Control Protocol (UDP/TCP) layer 112 and the GPRS Tunneling Protocol (GTP) layer 113. Between the MS and the GGSN there are the X.25 layer 114 and a second Internet Protocol layer 115. An application layer 116 in the MS will communicate with a peer entity that is located for example in another MS or some other terminal.
A typical negotiation that is required between peer entities in the mobile station and some of the fixed network devices is the eXchange IDentification or XID negotiation where the so-called L3CE (Layer 3 Compatibility Entity) parameters are agreed upon. L3CE as such is a protocol entity that is not separately shown in FIG. 1 but which will be located in the mobile station and either in a Radio Network Controller (RNC), a SGSN, or a GGSN on the network side for example as a part of or as a replacement to the SNDCP layer 108. The L3CE parameters will relate for example to the use of headers and data compression. The prior art method for arranging an XID negotiation is to insert the proposed L3CE parameters into certain messages on the LLC protocol layer and to use corresponding LLC-level answering messages to either acknowledge or reject the proposed L3CE parameters.
Proposals for the future UMTS (Universal Mobile Telecommunication System) have suggested similar protocol structures and negotiation arrangements for the communication between mobile stations, Radio Network Controllers (RNCs) and service nodes of packet-switched networks, with small changes or modifications in the designations of the devices, layers and protocols. It is typical to protocol structures like that in FIG. 1 that each layer has an exactly determined set of tasks to perform and an exactly determined interface with the next upper layer and the next lower layer. A certain amount of memory and processing power must be allocated in the devices taking part in the communication to maintain the layered structure and accomplish the tasks of each layer. It is therefore easily understood that the more complicated the structure of layered protocols, the more complicated the required software and hardware implementation. Complexity is disadvantageous in terms of costs incurred in design and manufacture and it increases the possibility of design errors. Additionally, in battery-driven mobile terminals it is a continual aim to reduce power consumption and diminish physical size, whereby a more simplified structure of protocol layers would create advantage.
It is therefore an object of the present invention to provide a method and arrangement that would accomplish the tasks of known communication protocol arrangements but with a simpler protocol structure.
The objects of the invention are accomplished by replacing certain parts of the protocol structure by transferring its functionalities to other parts of the protocol structure.
The method according to the first embodiment of the invention is characterised by that it comprises the steps of
creating a request message for requesting the setup of a new Packet Data Protocol context,
inserting into the created request message a set of suggested upper layer parameters,
transmitting the request message to the network device,
receiving from the network device a set of agreed upper layer parameters and
employing the agreed upper parameters within the new Packet Data Protocol context the setup of which was requested.
The method according to the second embodiment of the invention is characterised by that it comprises the steps of
creating an accept message for accepting a routing area update transmitted by the mobile station,
inserting into the created accept message a set of suggested upper layer parameters,
transmitting the accept message to the mobile station,
receiving from the mobile station a set of agreed upper layer parameters and
employing the agreed upper layer parameters within the Packet Data Protocol context which was subject to the handover.
The invention relates closely to the observation that the role of certain layers in many protocol structures is of minor practical value and is limited to certain measures for avoiding loss of data during a handover and exchanging certain parameters. This kind of layers may be completely omitted by combining their functions with suitable other existing parts of the protocol structure.
In the GPRS example presented in the description of prior art the protocol layer that can be omitted is the LLC layer. We may note that the RLC layer is capable of performing all required error correction tasks over the radio interface in normal operation and the role of LLC has mainly been related to handovers between different BSCs (Base Station Controllers), where error-critical (but not delay-critical) data has needed a mechanism for avoiding loss of data. In the proposed UMTS a similar need has existed in handovers between different RNCs or SGSNs (often designated as 3GSGSNs or 3rd Generation SGSNs). A method and arrangement for removing this need had been presented in the co-pending Finnish patent application number 982531, rendering the error-correcting functions of the LLC layer superfluous.
The LLC layer has also had certain responsibilities such as flow control and XID negotiation mentioned in the description of prior art. According to the invention the exchange of the suggested L3CE parameters and corresponding acknowledgements and/or rejections is implemented in the so-called PDP (Packet Data Protocol) context messages that belong to the SM layer and routing area update messages that belong to the MM layer in the protocol structure.